Pasquale Stefanizzi, Lorenza Moscara, Claudia Palmieri, Andrea Martinelli, Antonio Di Lorenzo, Chiara Scaltrito, Petra Buonvino, Francesca Oliveto, Giovanna Pice, Laura Marchisella, Giuseppe Spinelli, Silvio Tafuri
INTRODUCTION: Recombinant Zoster Vaccine (RZV) is recommended for Herpes Zoster (HZ) prevention in high-risk patients over 18 years of age. RESEARCH DESIGN AND METHODS: This is a prospective population-based study conducted over a three-year period in a Southern Italian General Hospital. The study population was represented by RZV recipients with diverse chronic comorbidities. Adverse Events Following Immunization (AEFIs), baseline disease flares and post-vaccination HZ episodes were evaluated through sequential follow-ups conducted 7 days, 3 months, and 3-38 months post-vaccination, respectively. RESULTS: Study population included 787 RZV recipients, mostly affected by onco-hematological, cardiovascular and rheumatological disorders. The AEFIs reporting rate was 44.15%. The most frequent symptoms were injection site pain/itching (37.19%), asthenia/malaise (12.74%) and fever (10.30%). Three serious AEFIs with consistent causal association with vaccination were recorded (0.22%), all of which underwent full recovery. Sixteen patients (2.37%) experienced a baseline condition flare-up within 3 months (mean interval 33.88 ± 24.88 days). Multiple baseline disorders (OR:1.97; 95%CI:1.37-2.83; p-value < 0.001) and rheumatological conditions (OR:11.67; 95%CI:2.00-68.27; p-value < 0.01) increased flare risk, while male sex decreased it. Twenty-six vaccinees manifested HZ post-vaccination (cumulative incidence rate 5.05/100,000 person-days), with particularly increased incidence in patients with recurrent/severe HZ history (IRR:14.35; 95%CI:5.64-34.04; p-value < 0.001). CONCLUSION: The study demonstrates RZV safety and HZ protection in vulnerable patients, consistently with available evidence.